Because Ethernet technology features low price and high expansibility, etc., it has evolved from a mainstream LAN technology to a primary data service access technology and is widely used in Metropolitan Area Network (MAN) by more and more telecom operators. Providing of Ethernet data services has becoming a trend for telecom operators. Ethernet data services can be classified into two types: Ethernet private line services and Virtual Local Area Network (VLAN) services.
For convenience, the phrases and abbreviations in the following description have the following meanings: MPLS—Multi-protocol Label Switching; GFP—General Frame Positioning; VLAN—virtual Local Area Network; VMAN—virtual Metropolitan Area Network; RPR—Resilient Packet Ring.
Currently, most of the telecom operators' data transmission networks are SDH/SONET networks. Therefore, it is a highlight for telecom operators and telecom equipment manufacturers to access and transfer Ethernet data frames effectively in a SDH/SONET network to meet the increasing demand for Ethernet data services. At present, several telecom equipment manufacturers have provided devices to access and transfer Ethernet data frames in an SDH/SONET network, and those devices may be classified into 3 types according to the implementation approach of functionality:
(1) Data mapping/demapping scheme;
(2) Bridge scheme;
(3) RPR scheme.
FIG. 1 shows a block diagram of an apparatus according to the data mapping/demapping scheme in the first prior art. The apparatus includes one or more subscriber network interfaces 20 (standard Ethernet interfaces), one or more inter-network interfaces 30 (synchronous digital transmission channels), one or more mapping/demapping devices 101, 102, . . . , each of which corresponds to a unique subscriber network interface and a unique inter-network interface. Wherein, data frames entering the apparatus via the one or more subscriber network interfaces 20 and data frames output from the apparatus comply with Ethernet data standard; data frames entering the apparatus via the one or more inter-network interfaces 30 and data frames output from the apparatus comply with synchronous digital transmission network standard.
Wherein the one or more mapping/demapping device maps Ethernet data frames entering the apparatus via the one or more subscriber network interfaces 20 to synchronous digital data frames, and output the mapped data frames via the one or more inter-network interfaces 30; further, the one or more mapping/demapping devices demap synchronous digital data entering the apparatus via the one or more inter-network interfaces 30 to Ethernet data frames, and output data frames via the one or more subscriber network interfaces 20. However, the functionality of the apparatus is simple, thus it can only provide Ethernet private line services.
FIG. 2A shows a block diagram of an apparatus utilizing the bridge scheme in the second prior art. The apparatus includes one or more subscriber network interfaces 20 (standard Ethernet interfaces), each of which corresponds to a unique bridge port. The apparatus further includes one or more inter-network interfaces 30 (synchronous digital transmission channels). The apparatus further includes a bridge device 400 (described in detail in IEEE802.1D and IEEE802.1Q), wherein the bridge device 400 includes a plurality of bridge ports, each of which corresponds to a unique subscriber network interface or a unique mapping/demapping device. Each mapping/demapping device corresponds to a unique bridge port and a unique inter-network interface. Wherein, data frames entering the apparatus via the one or more subscriber network interfaces 20 and data frames output from the apparatus comply with Ethernet data standard; data frames entering the apparatus from the one or more inter-network interfaces 30 and data frames output from the apparatus comply with the standard of synchronous digital transmission network.
The data frames entering the apparatus via the one or more subscriber network interfaces 20 enter the bridge device 400 via bridge ports corresponding to the one or more subscriber network interfaces 20 interface. The bridge device 400 calculates a bridge output port according to the address information in the data frames and sends the data frames to the corresponding mapping/demapping device 102 (the mapping/demapping device maps the data frames and then outputs them to the inter-network interface) via the output port, and vice versa.
In the bridge scheme, usually the operator is allowed to map partial or all subscriber network interfaces to mapping/demapping devices in a one to one way through configuration. In this case, the apparatus employs both of above technical schemes, so it is called an enhanced bridge scheme. The functional model of an enhanced bridge device is shown in FIG. 2B.
The disadvantage of the second prior art is:
(1) It is unable to provide integral VLAN service. If a plurality of subscribers are attached to the apparatus via the one or more subscriber network interfaces and there are conflicts among address spaces of Ethernet data frames of those subscribers, the apparatus is unable to isolate the conflicts effectively, thus it is unable to provide services correctly to those subscribers.
(2) A common bridge (non-enhanced bridge) is unable to provide Ethernet private line service.
(3) One subscriber network interface can only support one service type (Ethernet private line service or VLAN service), which limits the access capability of the apparatus. In some cases, though the processing capacity of the device is still sufficient enough, new devices have to be added to improve access capacity because the subscriber network interfaces have been used up.
(4) One inter-network interface can only support one service type (Ethernet private line service or VLAN service), which leads to low convergence capability of the apparatus. In some cases, in a star topology network, though the processing capacity of the apparatus is still sufficient enough, new devices have to be added to improve convergence capacity because the inter-network interfaces have been used up. For operators, it means not only new investment but also bandwidth waste.
FIG. 3 shows a block diagram of an apparatus utilizing the RPR scheme in the third prior art. The apparatus includes one or more subscriber network interfaces (standard Ethernet subscriber network interfaces), two inter-network interfaces (synchronous digital transmission channels), an RPR device 600 (described in IEEE802.17), two mapping/demapping devices, and a data processing device 500, which may be a data converging/diverging device or a bridge device.
Wherein the data frames entering the apparatus via the one or more subscriber network interfaces are processed as follows:
Step 1: the data processing device 500 processes the data frames (the data frames are converged if the data processing device is a data converging/diverging device; the data frames are switched if the data processing device is a bridge device);
Step 2: the data processing device 500 transfers the processed data frames to the RPR device 600;
Step 3: the RPR device 600 sends the data frames to the corresponding mapping/demapping device according to the address information in the data frames;
Step 4: the mapping/demapping device maps the data frames and sends them to outside of the apparatus via the corresponding inter-network interface.
The data frames entering the apparatus via the inter-network interface are processed as follows:
Step 1: the mapping/demapping device performs demapping operation for the data frames and transfers the demapped data frames to the RPR device 600;
Step 2: the RPR device 600 processes the data frames and then sends them to the data processing device;
Step 3: the data processing device 500 processes the data frames (the data frames are diverged if the data processing device is a data converging/diverging device; the data frames are switched if the data processing device is a bridge device);
Step 4: the data processing device 500 finds corresponding subscriber network interface according to the address information in the data frames and then outputs the data frames via the subscriber network interface.
The disadvantages of the scheme are:
(1) It is unable to provide Ethernet private line service and VLAN service at the same time. If the data processing device is a bridge device, it doesn't support Ethernet private line service; if the data processing device is a data converging/diverging device, it doesn't support VLAN service.
(2) It can only be used in a ring topology network.